Trunking radio communication systems (hereinafter designated “trunking systems”) are known. A trunking system includes a plurality of repeaters in a single site (communication area), and a plurality of radio client devices share multiple talk channels with the plurality of repeaters. Among trunking systems, there are some called dedicated control type, which have a dedicated control channel, and some called distributed control type, which do not have a dedicated control channel.
In a dedicated control type trunking system, one control channel is provided for one site. A radio client device requests a repeater having the control channel for location registration, and that repeater conducts location registration for the radio client device. After that, the radio client device sets an idle channel based on control information transmitted via the control channel, and communicates with another radio client device via the idle channel.
A distributed control type trunking system includes, for one site, one repeater called a collect repeater that conducts location registration of a radio client device. A radio client device requests the collect repeater for location registration, and the collect repeater conducts location registration for the radio client device, and sets a home repeater. After that, the radio client device sets an idle channel based on control information from the home repeater, and communicates with another radio client device via the idle channel.
Unexamined Japanese Patent Application Publication No. 2010-109505 and Unexamined Japanese Patent Application Publication No. 2010-136350 disclose technology related to a distributed control type trunking system. With the radio communication system disclosed in Unexamined Japanese Patent Application Kokai Publication No. 2010-109505, in the case where a situation occurs in which operation stops at the home repeater, a secondary repeater acquires the home repeater's control information and conducts a repeater process as a proxy for the home repeater. In the radio communication system disclosed in Unexamined Japanese Patent Application Kokai Publication No. 2010-136350, in the case where a radio client device is able to receive a downlink signal from a home repeater but an uplink signal does not reach a repeater that provides an idle channel, the radio client device transmits a signal requesting communication with a peer radio client device on the same frequency as the frequency of the downlink signal from the home repeater.
With a dedicated control type trunking system, in one site, the repeater that has the control channel is unable to conduct location registration for another radio client device while conducting location registration for a given radio client device. Also, with a distributed control type trunking system that includes one collect repeater for one site, the collect repeater in one site is unable to conduct location registration for another radio client device while conducting location registration for a given radio client device. For this reason, in the case where a plurality of radio client devices request location registration at the same time in one site, it is necessary to successively conduct location registration for the plurality of radio client devices one at a time, and it takes time to complete location registration for the plurality of radio client devices.